Inclosed fuse



Nov. 2 1926. 1,605,543

L. C. HA RT INCLOSED FUSE Filed April 24, 1925 Patented Nov. 2, 1926.

UNITED STATES 1,605,543 PATENT OFFICE.

LESTER C. HART, OF CLEVELAND, OHIO, ASSIGNOR T0 HI-VOLTAGE EQUIPMENT COMPANY, A CORPORATION OF PENNSYLVANIA.

INCLOSED FUSE.

Application filed a ruaa, 1925. Serial No. 25,539.

The invention relates to fuses, and particularly to fuses of the expulsion type in which the fuse is carried or housed in a tube or a tubular member. It has for one of its principal objects, the provision of a fuse of the type specified, which is reliable under all conditions of service, and which will operate either with a light overload current, or with a very heavy overload without destroying any of the parts other than the fuse wire itself. It has for a further and most important object the provision of a construction which will unfailingly secure an extinction of the are after the fuse has blown. The fuse is illustrated and described in one relation, namely, a with an upright mounting, but may be used in other relations and in other positions depending upon conditions. In the embodiment of the invention illustrated:

. Figure 1 is a perspective view of the parts in assembled relation. And Fig. 2 is an enlaiiged longitudinal section through the fuse tu e.

Referring to the drawings, 1 is a base plate carrying the insulator posts 2 and 3, upon which are mounted the insulators 4 and 5. These insulators are provided with the metal caps 6 and 7, which constitute the terminals of the mains 8 and 9.

The cap or terminal 7 has rigidly secured thereon the metal yoke 10 having at one end the hooks 11, and at the other end, the split collar 12 clamped around the fuse tube, as indicated in Fig. 1. The fuse tube is made up of the casing 13 of metal and the tube 14 of insulating material, which latter is threaded into the casing 13. The casing 13 is provided with a pair of laterally pro ecting lugs 15 carried in the hooks 11. The lug and hook connections 11 and 15 in connection with the split collar 12 provide a convenient means for securing the tube in position and releasing it.

The casing 13 is closed by means of the plug 16, also of metal, which carries the lug 17 in which-is mounted the binding screw 18. This screw clamps the end of the fuse wire 19, such fuse wire extending through the tube 14 and being connected at its end to the terminal or cap 6 and to the main 8. The fuse wire is preferably smaller in cross sec.- tion at the end in the casing 13 than elsewhere, so that in case of an overload, this portion of the wire is burned out first, forming a vapor in the chamber 20, and develop- 1n g a pressure high enough to blow out any wire remaining in the tube and clear it of gases with a considerable degree of explosive force. The use of the smaller cross section of fuse wire (somewhat exaggerated in the drawing) 1n the chamber 20 facilitates this which, at the same time, has high insulating qualities. These requirements are met by the use of bakelite, reinforced by layers of canvas or paper.

In order to protect the bakelite from the heat generated by the electric arc, which is formed momentarily when the fuse blows, a liner 21 of refractory material, such as asbestos is provided. This liner, being protected by its position inside the tube, does not need to possess the weathering qualities of the tube itself.

It will be noted that the fuse wire is supported in the chamber. 20, so that it does not contact with the wall of the casing, which arrangement renders the wire more reliable as to the fusing point for which it is designed than would be the case if it were allowed to touch the metal wall of the casing, it bein recognized that a fuse wire surrounded an insulated by quiet air is accurate in its action in accordance with its calibration, but that this is not the case, if it engages aconductor.

The device has suflicient strength to withstand viole'nt explosions as developed by heavy sudden loads, and at the 'same time, the air space in the tube is so proportioned that when the device blows from a relatively" light overload, suflicient pressure and velocity is developed to insure a successful breaking of the are, which is formed, thus fulfilling the requirement for certainty of operation under the widest possible range of conditions.

The air gap, which is provided between the open end of the fuse tube 14 and the terminal 6, prevents the leakage of any ourrent through the tubeor over it after the fuse blows, and the force of the explosion is such as to insure the clearing of the tube and the extinguishing of the are, this action also being promoted by locating the terminal 6 out of alignment with the tube, so that the force of the explosion is directed over and away from the terminal, rather than against it. After the fuse has blown, the tube may be used again, the only part requiring replacement being the fuse wire.

What I claim is:

1. A fuse construction comprising a tube closed at one end and open at the other, supporting means at said closed end only, a fuse wire extending from the closed end of the tube out through the open end of the tube, a terminal lying at a substantial distance to one side of the line of the tube and spaced away from the end thereof to provide a complete air gap between the tube end and the terminal when the wire is'fused,

' to which terminal the fuse wire is connected,

a second terminal, and an electrical connee: tion between such second terminal and the end of the fuse wire lying in the tube, the space between the open end of the tube and the first mentioned terminal being free from any solid body aside from said wire.

2. In combination, a base, a pair of parallel insulator posts projecting from said base, an insulator mounted on each of said posts, each provided at its outer end with a metal terminal, a fuse tube'mounted at one end which is closed upon one insulator and with its other end open and extending laterally to a point at one side of the other terminal, but spaced away therefrom to provide a complete air gap between the tube and said other terminal and the inslflator supporting it, and a fuse wire extending through the tube with one end having electrical connection with the terminal on the insulator carrying the tube and with its other end extending out through the open end of the tube where it turns laterally and is connected to said other terminal the space betweenthe tube end and said other terminal being free from any solid body aside from the fuse wire.

3. In combination, a pair of parallel insulatorsupports in spaced relation, aninsulator carried on each of said supports, a terminal carried by each insulator, a fuse tube closed at one end and open at the other, mounted on one of said insulators at its closed end and extending transversely of said supports with its open end adjacent to the terminal on the other insulator, but unsupported by said last terminal or its insulator and out of alignment with such terminal, and a fusewire extending through the tube with one end lying in the closed end o the tube and having electrical connection with one terminal and with its other end extending out through the open end of the tube where it turns laterally and is connected to the other terminal, the space between the said open end of the tube and said other terminal being free from any solid body aside from the wire, thus giving a complete air gap when the wire is fused.

In testimony whereof,'I have hereunto subscribed my name this 16th day of April,

LESTER C. HART. 

